Preparation And Electrochemical Properties Of Nickel, Cobalt, Manganese Composite Oxide And Iron Oxide Anode Materials

Metal oxide anode materials are with suitable voltage platforms and high specific capacities.However,the poor electronic conductivity and large volume change during discharge-charge processes hurts their electrochemical properties.In this paper,sulfuration treatments and three-dimensional architecture is for improving the conductivity,different components and specific morphologies for enhancing the cycling stability,and high activation current for optimizing the solid electrolyte interphase.Moreover,the sodium storage properties of the prepared materials are evaluated,in consideration of the similarity of physicochemical properties between lithium and sodium.Various materials including MnCo₂O_4.5 nanoarrays,NiCo₂O₄ nanosheets and NiCo₂S₄ nanocones are of in-situ growth on the nickel foam with hydrothermal methods.They,as additive-free anodes for Li-ion batteries,show high initial lithiated capacities of 1533,1834,1833 mAh g^-1 at the current density of 0.1 A g^-1and corresponding coulombic efficiency of 60.4%,76.7%,87.4%,respectively.The sulfides,with less electronegativity to promote Li⁺migration,exhibit better activity and reversibility of electrochemical reactions,but,accompanied by an unwanted improvement of voltage platforms.Thus,the oxides are more appropriate anode materials,considering with cathodes for full cells to achieve higher output voltages and specific energy density.As a result,NiCo₂O₄ nanosheets show good rate capabilities and cycling performance,including 1279,952,657 mAh g^-1 at 1,2,4 A g^-1,respectively,and 1092 mAh g^-1 after 100 cycles at 0.5 A g^-1.The multi-component oxides of(Ni_xCo_yMn_1-x-y)₃O₄ with mesoporous microsphere morphologies are prepared by coprecipitation as conversion-type anode materials,and their element content adjusted to optimize the lithium storage performance.As a result,the optimized(Ni_0.1Co_0.3Mn_0.6)₃O₄ LIB anodes exhibit good electrochemical stability,including 851 mAh g^-1 after 500 cycles at 0.5 A g^-1(vs 39 mAhg^-1 after 100cycles at 0.5 A g^-1 for(Ni_0.3Co_0.3Mn_0.4)₃O₄ anodes)and 501 mAhg^-1 after 1500cycles at 1 A g^-1 with capacity retention of 69.3%（vs the values of activated electrodes）,attributed to the synergistic effect of various metals,shorter transmission path of lithium ions and enhanced stress release of material architectures while better crystal structure,faster Li⁺diffusion and more stable SEI layer.NiCo₂O₄ materials with various morphologies of mesoporous microspheres,voidless microspheres and nanoplates are tailored to investigate the capacity loss mechanisms of metal oxide anodes for LIBs.The data of their morphology evolution in discharge-charge processes suggests two kinds of capacity fading mechanisms:（i）material pulverization that the mesoporous microspheres of loose primary particle accumulation broken up due to volume swing,leading to increased polarization and less electric contact of active materials;（ii）the inhibition of electrochemical reactions that the voidless microspheres and nanoplates blocked by thick SEI layer.The designed material structures of nanoparticles and hollow microspheres with enhanced electrolyte diffusion and strain accommodation and the optimized SEI layer by choosing proper activation methods are for high-performance metal oxide anodes for LIBs.As a result,Fe₂O₃ hollow microsphere anodes show the lithiation capacity of 829 mAh g^-1 after 1000 cycles at 1 A g^-1 with capacity retention of 92%.The sodium storage properties of the prepared materials are evaluated.The results suggest a great distinction between Li⁺and Na⁺storage performance of the metal oxide anodes,associated with different structure and properties of SEI layer and different activity and reversibility of electrochemical reactions.The full cells,assembled with prepared high-performance anodes also exhibit good electrochemical properties.